The current use of Etch Rate Monitor Wafers (ERMW), while inexpensive and well known, is a cumbersome technique to debug a recipe with a series of etch conditions. In current best known practices film thickness is measured on a wafer before and after processing. The etch rate is inferred as the thickness change against the perceived etch-step time(s) and thus measures an integral of all the material removed. While the current method provides for very detail and accurate maps, it does not give insight as to at what step the etch really took place. Furthermore, modern etch recipes may contain up to a dozen etch steps that all interact to give the composite etch profile. To debug this using an ERMW may take many runs using a divide and conquer strategy. This is expensive and time consuming.
It is within this context that aspects of the present disclosure arise.